U.S. patent number 4,300,807 [Application Number 06/046,741] was granted by the patent office on 1981-11-17 for method and device for balancing rotary bodies with passive radial and active axial magnetic suspension and for orienting their axis of rotation.
This patent grant is currently assigned to Societe Nationale Industrielle Aerospatiale. Invention is credited to Pierre Poubeau.
United States Patent |
4,300,807 |
Poubeau |
November 17, 1981 |
Method and device for balancing rotary bodies with passive radial
and active axial magnetic suspension and for orienting their axis
of rotation
Abstract
A method and device for balancing magnetically suspended bodies
wherein at the axial ends of the bodies are included two centering
devices on the rotor side constituted by centered and excentric
magnetic rings facing two centering devices on the stator side with
centered and excentric magnetic rings, the magnetic field in the
air gaps between the pairs of rings being made variable according
to signals received from correction sensors of the axes and of the
alignment.
Inventors: |
Poubeau; Pierre (Le Pecq,
FR) |
Assignee: |
Societe Nationale Industrielle
Aerospatiale (FR)
|
Family
ID: |
9209357 |
Appl.
No.: |
06/046,741 |
Filed: |
June 8, 1979 |
Foreign Application Priority Data
|
|
|
|
|
Jun 12, 1978 [FR] |
|
|
78 17457 |
|
Current U.S.
Class: |
310/90.5;
310/83 |
Current CPC
Class: |
F16C
32/0444 (20130101); G01M 1/30 (20130101); F16C
32/0476 (20130101) |
Current International
Class: |
G01M
1/30 (20060101); G01M 1/00 (20060101); F16C
039/06 () |
Field of
Search: |
;308/10
;310/83,112,114-117 ;74/5.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Skudy; R.
Attorney, Agent or Firm: Flocks; Karl W. Starobin; A.
Fred
Claims
I claim:
1. Method of balancing a rotary body with a stator, rotor and
passive radial and active axial magnetic suspension and of
orienting its axis of rotation, consisting of arranging at ends of
said stator and rotor, pairs of magnetic rings facing each other
with an air gap between them and with an axial field in said air
gap, said magnetic rings being excentric on said rotor and
concentric on said stator for placing in coincidence the axis of
inertia with the rotor axis, said magnetic rings being concentric
on said rotor and excentric on said stator for the orientation of
the axis of rotation, the correction being obtained by variation of
the induction on said magnetic rings of said stator.
2. Method of balancing according to claim 1, in which rings of said
rotor side are excentric.
3. Method of balancing according to claim 1, in which rings of said
stator side are excentric.
4. Method of balancing according to claim 1, comprising a return
pole piece for the magnetic flux.
5. Method of balancing according to claim 1, comprising:
a radially magnetized annular magnet on said stator;
ferromagnetic rings enclosing said magnet;
and a mechanical means linked to said magnet for varying the
separation of said air gap by axial translation of said magnet and
of said rings on said stator.
6. Method of balancing according to claim 1, comprising:
a radially magnetized annular magnet on said stator;
ferromagnetic rings enclosing said magnet;
a magnetic shunt placed in front said magnet;
and a mechanical means linked to said shunt for varying the
separation between said magnetic shunt and said magnet by axial
translation of said shunt.
7. Method of balancing according to claim 1, comprising:
an annular magnet with radial flux on said stator;
ferromagnetic rings enclosing said annular magnet;
a return pole piece on said stator, and
a winding on said return pole piece; an adjustment of the current
sent to said winding, the flux being closed on itself through said
return pole piece and said rings on said stator permitting the
magnetic field to be varied in the air gap between each of said
centered ring and excentric ring pairs.
8. Method of balancing according to claim 1, comprising:
a return pole piece on said stator;
a flux closing return pole piece on said rotor;
a winding on said return pole piece on said stator;
an adjustment of the current sent to said winding, the flux closing
through said flux closing return pole piece on said rotor,
permitting the magnetic field to be varied in the air gap between
each of said centered ring and excentric ring pairs.
9. Method of balancing according to claim 1, comprising an electric
motor and a worm screw and thread actuated by said electric motor,
in order to drive the stator ring concerned axially.
10. Method of balancing according to claim 6, comprising an
electric motor and a worm screw and thread actuated by said motor,
in order to drive said magnetic shunt concerned axially.
11. Method of balancing according to claim 1, comprising conducting
rings fast to said rotor and fixed electromagnetic detectors which
are arranged radially along the axes x and y for the alignment of
the axis of rotation and in another radial direction for placing
the axis of inertia and the rotor axis in coincidence at a short
distance from said conducting rings to produce, by impedance
detection adaptation signals of a correction control current.
12. Method of balancing according to claim 11, comprising an axial
mark for producing an angular reference pulse signal.
13. Method of balancing according to claim 1 in which said rotary
body is of conformation C/A.ltoreq.1 in which C is the moment of
inertia around the axis of rotation merged with an axis of inertia
and A is the moment of inertia around the transverse axes of
inertia.
14. Method of balancing according to claim 1, in which said rotary
body is of conformation C/A.gtoreq.1 in which C is the moment of
inertia around the axis of rotation merged with an axis of inertia
and A is the moment of inertia around transverse axes of
inertia.
15. Apparatus for balancing a rotary body and orienting its axis of
rotation comprising a stator; rotor; and passive radial and active
axial magnetic suspension including pairs of magnetic rings
arranged at ends of said stator and rotor facing each other with an
air gap between them and with an axial field in said air gap, said
magnetic rings being excentric on said rotor and concentric on said
stator for placing in coincidence the axis of inertia with the
rotor axis, said magnetic rings being concentric on said rotor and
excentric on said stator for the orientation of the axis of
rotation; and means to vary the induction on said magnetic rings of
said stator to obtain a correction for the coincidence and
orientation.
16. The apparatus for balancing according to claim 15, comprising
one ring of said pair of magnetic rings being a yoke shaped flux
closing pole piece for the magnetic flux.
17. The apparatus for balancing according to claim 15, futher
characterized by
said magnetic suspension including
a radially magnetized annular magnet on said stator,
ferromagnetic rings enclosing said magnet;
and said induction varying means including
a mechanical means linked to said magnet for varying the separation
of said air gap by axial translation of said magnet and of said
rings on said stator.
18. The apparatus for balancing according to claim 15, further
characterized by
said magnetic suspension including
a radially magnetized annular magnet on said stator,
ferromagnetic rings enclosing said magnet,
a magnetic shunt placed in front of said magnet,
and said induction varying means including
a mechanical means linked to said magnet for varying the separation
between said magnetic shunt and said magnet by axial translation of
said shunt.
19. The apparatus for balancing according to claim 15, further
characterized by
said magnetic suspension including
an annular magnet with radial flux on said stator,
ferromagnetic rings enclosing said annular magnet,
a return pole piece on said stator,
a winding on said return pole piece,
said induction varying means including
a means of adjustment of the current sent to said winding, the flux
being closed on itself through said return pole piece and said
rings on said stator permitting the magnetic field to be varied in
the air gap between each of said centered ring and excentric ring
pairs.
20. The apparatus for balancing according to claim 15, further
characterized by
said magnetic suspension including
a return pole piece on said stator,
a flux closing return pole piece on said rotor,
a winding on said return pole piece on said stator,
said induction varying means including
a means of adjustment of the current sent to said winding, the flux
closing through said flux closing return pole piece on said rotor,
permitting the magnetic field to be varied in the air gap between
each of said centered ring and excentric ring pairs.
21. The apparatus for balancing according to claim 15, further
comprising an electric motor and a worm screw and thread actuated
by said electric motor, in order to drive the stator ring concerned
axially.
22. The apparatus for balancing according to claim 18, further
comprising an electric motor and a worm screw and thread actuated
by said motor, in order to drive said magnetic shunt concerned
axially.
23. The apparatus for balancing according to claim 15, further
comprising conducting rings fast to said rotor and fixed
electromagnetic detectors which are arranged radially along the
axes x and y for the alignment of the axis of rotation and in
another radial direction for placing the axis of inertia and the
rotor axis in coincidence at a short distance from said conducting
rings to produce, by impedance detection adaptation signals of a
correction control current.
24. The apparatus for balancing according to claim 23, further
comprising an axial mark for producing an angular reference pulse
signal.
25. The apparatus for balancing according to claim 15, in which
said rotary body is of conformation C/A.ltoreq.1 in which C is the
moment of inertia around the axis of rotation merged with an axis
of inertia and A is the moment of inertia around the transverse
axes of inertia.
26. The apparatus for balancing according to claim 15, in which
said rotary body is of conformation C/A.gtoreq.1 in which C is the
moment of inertia around the axis of rotation merged with an axis
of inertia and A is the moment of inertia around transverse axes of
inertia.
Description
1. Field of the Invention
The problems associated with the rotation of solid bodies generally
are of two types. One consists of making the axis around which the
rotor rotates coincide with an axis of inertia in said body to
balance it by causing the imbalances to disappear and the second is
aimed at orienting the axis of rotation in a predetermined
direction.
Sometimes, these two adaptations are effected conjointly when it is
desired, for example in a satellite, on the one hand, to balance
two momentum wheels arranged in counter-rotation on a common axis
and, on the other hand, to control the perfect alignment of the
kinetic moments of the momentum wheels.
In rotary bodies centered by the contact of materials such as ball
bearings or pivots, balancing is achieved by the material
displacement of the element of the bearing borne on the rotor side
with respect to the rotor or by the addition or withdrawal of
so-called balancing weights, this action having to be carried out
according to the angular rotary speed of said rotary body, when the
speed variation introduces modification in the position or the
orientation of the axis of inertia concerned.
In the same way, these same rotary bodies experience a modified
orientation of their axis of rotation if the bearings are displaced
mechanically with respect to their supports assumed fixed by
definition.
In practice, these operations are difficult to carry out especially
in the course of rotation.
As regards magnetic bearings in which material contacts are
eliminated, static and dynamic balancing may be achieved either by
adjusting balance weights, or by corrections due to magnetic fields
operating from sensors, said magnetic fields being also able to
intervene to adapt the orientation of the above-mentioned axis of
rotation.
2. Description of the Prior Art
According to the types of suspensions comprised in the invention
and which have been particularly developed by Applicant, notably as
disclosed in his U.S. Pat. No. 3,955,858 of May 11, 1976, and in
his U.S. patent applications No. 886,496 filed on Mar. 14, 1978,
now U.S. Pat. No. 4,211,452 and No. 929,077 filed on July 28, 1978
the bearings are magnetic centering rings ensuring passive radial
stiffness with the normally axial magnetic field in the air gap and
active axial centering is ensured by magnetic fields of coils
slaved to a detector.
It should be noted that the term "magnetic centering ring" used in
the present description must be taken in a particular sense.
In fact, in air gaps, which extend perpendicularly to the axis of
rotation, it is rings of lines of magnetic force, hence variable in
magnitude and direction as a function of the magnetic induction,
which effect the coupling means, hence the radial centering means
between rotor and stator.
It results therefrom that it is the pairs of rings which then
procure, as material elements, the magnetic field necessary for
said centering, said magnetic field being also producible in said
rings by permanent magnets or again electromagnets.
In the previously mentioned systems of Applicant, the pairs of
magnetic centering rings are all concentric and their number is
determined by the value of the radial stiffness imposed according
to the case concerned.
In these systems, the position of said pairs of magnetic centering
rings fixed to the rotor defines a "rotor axis" around which said
rotor rotates; that is to say when the effects of inertia are
neglected, the points of this axis and these alone have a zero
rotary speed and balancing consists of making the "rotor axis"
coincide with the inertia axis.
In the same way, the position of said fixed magnetic centering
rings on the stator defines the orientation which is imposed in
space on "the rotor axis" and any variation in position imposed on
said rings results correlatively in a change in orientation of said
"rotor axis".
It is an object of the present invention to provide for the systems
concerned, that is to say for systems including pairs of passive
radial centering rings and an active axial centering device slaved
to a detector, a method and a corresponding device for, when the
spacings are relatively small, on the one hand, balancing their
rotor by bringing its axis of rotation to the axis of inertia and,
on the other hand, to orient said axis of rotation in a
predetermined direction.
GENERAL DESCRIPTION OF THE INVENTION
In accordance with the invention, the pairs of magnetic centering
rings are made excentric with respect to one another so that it is
the above-mentioned rings of lines of force which determine,
according to the value of the induction produced, the resulting
centering.
In a way, on the choice of the value of magnetic induction applied
to a given pair of rings, will depend the value imposed on the
desired correction, whether it relates to the correction applying
to the rotor axis itself with respect to the axis of inertia
concerned or to its orientation in space.
Of course, the variation of induction can be produced in various
ways among which it is possible to resort to: variation of the air
gap, the influence of a magnetic shunt or the regulation of a
current in a coil.
Other characteristics, advantages and features of the present
invention will become apparent from the description given below
with reference to the accompanying drawings illustrating, by way of
explanation and in purely non-limiting manner, various possible
embodiments of means for the application of the method according to
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In these drawings:
FIG. 1 is a diagrammatic sectional view, recalling the mechanical
conditions of balancing and of orienting rotary bodies;
FIGS. 2A and 2B are diagrammatic sectional views showing the
possible corrections of static and dynamic balancing of rotary
bodies;
FIG. 3 is a diagrammatic view of two momentum wheels in
counter-rotation;
FIG. 4 is a diagrammatic view showing the means of rotation
correction which can be applied, in accordance with the invention,
when the rotary body is characterized by the relationship
C/A.ltoreq.1, in which C is the moment of inertia around the rotary
axis merged with an axis of inertia and A is the moment of inertia
around the transverse axes of inertia;
FIG. 5 is a diagrammatic view showing the rotation correction means
which can be applied, in accordance with the invention, when the
rotary body is characterized by the relationship C/A.gtoreq.1, in
which C is the moment of inertia around the axis of rotation merged
with an axis of inertia and A is the moment of inertia around the
transverse axes of inertia;
FIGS. 6A, 6B, 6C and 6D are diagrammatic views in section and
viewed in a flattened plane of concentric and excentric magnetic
ring centering elements for the application of the method according
to the invention, it being noted that FIGS. 6A, 6B relate to stator
rings and FIGS. 6C and 6D rotor rings;
FIGS 7A and 7B are views in partial axial section showing a pair of
air gap variation magnetic rings, according to two possible
embodiments, for the closing of the magnetic flux; FIGS. 8A and 8B
are views in partial axial section showing a pair of movable shunt
magnetic rings, according to two possible embodiments for the
closing of the magnetic flux;
FIGS. 9A and 9B are views in partial axial section showing a pair
of magnetic rings with electromagnetic variation of the flux,
according to two possible embodiments, for the closing of the
magnetic flux;
FIG. 10 is a view in radial section of a wheelworm screw mechanism
to enable actuation of the rings or of the magnetic shunt; and
FIG. 11 is a view in partial section along the line XI--XI of the
mechanism according to FIG. 10.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1, it is seen that, according to the laws of
mechanics, all rotating bodies have an axis of inertia .phi.-.phi.'
and a "rotor axis" z-z' oriented in a direction Z-Z'.
The balancing of the body consists therefore of bringing into
coincidence the axes .phi.-.phi.' and z-z' and of displacing the
bed or seating of the bearings, on the stator side, if it is
desired to obtain the required orientation Z.sub.1, Z'.sub.1.
This bringing into coincidence can be achieved in two different
ways: one, according to FIG. 2A, which consists of moving the
bearing supports on the rotor itself, from the positions shown in a
dashed line to the position in solid line; the other according to
FIG. 2B, which provides for the addition (or the withdrawal) of a
balancing weight M.sub.1, when the axes of inertia and of the rotor
are parallel, or M.sub.2, M.sub.3 when these axes are not
parallel.
FIG. 3 shows by way of indication, the advantage which can be
offered by the change in orientation of a rotor axis Z-Z' on the
common axis Z.sub.1 -Z'.sub.1 -Z.sub.2 -Z'.sub.2 of two momentum
wheels R.sub.1, R.sub.2 mounted in counter rotation, on a
satellite, for example.
If the systems including material connections by ball bearings or
pivots of FIGS. 1, 2A and 2B can be corrected in the known manner
recalled above, it is different as regards rotary bodies suspended
magnetically in accordance with the invention which, themselves,
can only be corrected by actions on the magnetic fields.
FIGS. 4 and 5 show the general aspects under which magnetic
suspension devices within the scope of the invention are generally
encountered.
In FIG. 4, the rotary body 1 is characterized by the relationship
C/A.ltoreq.1 and it is provided at its ends with rotor centering
elements 2-3 and stator centering elements 4-5 ensuring radial
inflexibility whilst an axial actuator 6 (not involving the
invention) is shown diagrammatically for memory.
In FIG. 5, the rotary body 7 is characterized by the relationship
C/A.gtoreq.1. It is provided at its ends with rotor 2-3 and stator
4-5 centering elements of the same type ensuring radial stiffness
whilst the axial actuator 6 is also shown diagrammatically for
memory.
Prior to the present invention, the rings of the lines of force
existing in the air gaps 8 and 9 were all concentric with the rotor
axis z-z', which was not necessarily in coincidence with the axis
of inertia .phi.-.phi.', which was manifested by phenomena of
imbalance and of vibration encountered which had to be corrected by
balancing.
In accordance with the invention, the centering elements include,
on the one hand, magnetic rings centered with respect to Z-Z' and,
on the other hand, rings excentric with respect to Z-Z', for which
the magnetic induction regulation enables modification of the rings
of lines of force of the air gap so that the rotor axis can be
brought into coincidence with the axis of inertia and/or the axis
of rotation can be brought into a predetermined direction.
Thus, in FIGS. 6A, 6B, 6C and 6D, the region of magnetic rings and
the possible orientation of the lines of force in the air gap E,
are shown symbollically,
In these figures, the centering element of FIGS. 6A, 6B is
connected to the stator and the concentric magnetic rings of center
O are arranged along C.sub.10, C.sub.20, C.sub.30, C.sub.40.
In FIGS. 6D, 6C, the centering member is connected to the rotor and
the concentric magnetic rings of center O' are arranged along
C'.sub.10, C'.sub.20, C'.sub.30, C'.sub.40.
In FIGS. 6A, 6B, the other rings are excentric along O.sub.1 for
C.sub.1, O.sub.2 for C.sub.2, O.sub.3 for C.sub.3 and O.sub.4 for
C.sub.4.
In FIGS. 6D, 6C, the other rings are excentric along O'.sub.1 for
C'.sub.1, O'.sub.2 for C'.sub.2, O'.sub.3 for C'.sub.3 and O'.sub.4
for C'.sub.4. The excentering of the rings, which must remain
small, determines a correcting domain which is represented by a
square d.sub.1 in FIG. 6A and a square d.sub.2 in FIG. 6D, but
which could be quite different such as rectangular, for
example.
At the level of the air gap the restoring forces, which are
determined by the induction in the rings, define the centering
according to one embodiment which will be explained below. If the
two rings C'.sub.1, C'.sub.2 on the rotor side and C.sub.10,
C.sub.20 on the stator side are isolated, said rings being of the
same diameter but excentric along O'.sub.1 for C'.sub.1 and
O'.sub.2 for C'.sub.2, the middle of O'.sub.1, O'.sub.2 being O',
it is observed that when the rotor side rings C'.sub.1, C'.sub.2
are held by axial slaving opposite the stator side rings C.sub.10,
C.sub.20, they are centered according to the restoring forces shown
diagrammatically by the arrows F.sub.1, F.sub.2 in the air gap
which are exerted respectively between the two pairs of rings
C'.sub.1, C'.sub.2 -C.sub.10, C.sub.20. If the stator ring C.sub.20
is eliminated, which corresponds to a zero radial stiffness for the
pair C'.sub.2 -C.sub.20, O'.sub.1 is positioned opposite O' center
of the stator side rings and as a result the rotor axis then passes
through O'.sub.1. If, on the other hand, C'.sub.1 is removed, it is
O'.sub.2 which is centered opposite O' and the rotor axis passes,
this time through O'.sub.2.
If the radial stiffness of the pairs C'.sub.1 -C.sub.10, C'.sub.2
-C.sub.20 can be controlled from the stator, the orientation of the
rotor axis and its positioning with respect to the center of
gravity result therefrom and the point of passage of the rotor axis
at the level of the bearing constituted by C'.sub.1 -C.sub.10 and
C'.sub.2 -C.sub.20 can sweep the segment O'.sub.1, O'.sub.2.
A second set of stator side rings C.sub.30 -C.sub.40 concentric
with C.sub.10 -C.sub.20 and two rotor side rings C'.sub.3, C'.sub.4
excentric for example in a perpendicular direction, of center
O'.sub.3 -O'.sub.4, act in the same way previously, so that the
group of rings enables the point of the rotor axis to be moved,
substantially within a square d.sub.2 centered at O' and whose side
is equal to O'.sub.1, O'.sub.2 (or O'.sub.3, O'.sub.4).
The complete suspension of a rotary body hence necessitates two
bearings with centering members and the balancing consists of
adjusting the centers of rotation of the two bearings, as indicated
above, so as to bring each these two points on to the axis of
inertia around which the rotation must be effected, which
corresponds in fact to the placing of the axes .phi.-.phi.' and
z-z' in coincidence.
Such a bringing into coincidence necessitates magnetic rings or
rings of concentric lines of force on the stator and excentric on
the rotor and the adaptation of the inductions on the stator rings
enables the .phi..fwdarw.z optimal stiffness, enabling the
correction desired, to be determined.
Modification of the orientation of the axis of rotation is effected
similarly to that which has been described above but in this case,
it is the concentric rings which are on the rotor and the excentric
rings which are on the stator. In a way, and according to FIGS. 6A
to 6D, the concentric rings of the rotor will permit the
displacement of the rotor axis or axis of rotation, in a direction
determined by the magnetic fields of the excentric rings of the
stator and this, in a domain of correction determined by the square
d.sub.1 whose side is represented by the centers O.sub.1, O.sub.2
(or O.sub.3, O.sub.4).
It is seen thus that the rotor and stator centering members which
have been shown in FIGS. 6A, 6D with conjointly concentric and
excentric rings, can ensure the correction of the rotor axis and of
the orientation of this rotor axis at the same time.
It is obvious that it would be, a fortiori, possible to use only
one correcting system on the two, without departing however from
the scope of the invention.
The adaptation of the magnetic fields in the air gaps requires the
modification of the magnetic inductions on the generating rings of
these fields. Firstly, these magnetic fields can be generated in
different ways, as for example those shown diagrammatically in
FIGS. 7A, 7B; 8A, 8B and 9A, 9B. It is to be noted that, in these
figures, the elements shown on the left of the axis XX.sub.1, are
coupled to the stator whilst the elements shown on the right of
this axis XX.sub.1 are coupled to the rotor.
In FIG. 7A, the lines of force C result from the action of the
magnets 10, 11 with radial fields closing through ferromagnetic
rings 12-13 and 12'-13' and the air gap is, in the present case,
adapted according to E.sub.1, E.sub.2, E.sub.3 . . . by a mechanism
14 which will be described in detail below.
In a modification, in FIG. 7B, the magnet 11 connected to the rotor
is replaced by a reclosing yoke 15 for the flux or return pole
piece.
In FIG. 8A, the lines of force C result from the operation of
magnets 16, 17 with radial magnetization reclosing through
ferromagnetic rings 18, 19, 18', 19' and the variation in field S1,
S2, S3, . . . is generated by magnetic shunts 20 controlled by a
mechanism 14 which will be also described below, the shunts 20
being on the stator portion in the same way as the rings on which
they act directly.
In a modification, in FIG. 8B, the magnet 16, connected to the
rotor, is replaced by a reclosing yoke 22 for the flux or return
pole piece.
In FIG. 9A, the lines of force C result from the operation of a
coil 23 on the stator and of a magnet 24 on the rotor and the flux
is closed, on the one hand, through a coiled yoke or wound pole
piece 25 and on the other hand, by ferromagnetic rings 26, 27 and
through the magnet 24.
As a modification, in FIG. 9B, the magnet 24 connected to the rotor
is replaced by a flux closing pole piece 29.
As regards variation in magnetic induction to be produced in the
regions of the magnetic rings according to FIGS. 6A, 6B, 6C and 6D,
the mechanical means 14 applicable according to FIGS. 7A, 7B and
8A, 8B, can result from the device shown by way of example in FIGS.
10 and 11. The movable parts, sliding axially in suitable circular
grooves, are connected to linking rings 21 fast to a circular part
30 provided with a thread 30A engaged in the threaded portion of a
body of a mechanism 31 connected to the stator.
The circular part 30 is rotated by a worm screw meshed on the tooth
portion 30B so that its rotation results in its axial movement
through the effect the threaded part.
A motor 33 actuating the worm screw 32 is supplied from a sensor
system which will be discussed below.
It is the same for the coil current 23 which is actuated from the
same sensors. The sensors which have just been discussed, have
essentially two functions; one, for the correction of the axis of
inertia with respect to the rotor axis and the other, for the
alignment of said rotor axis in coincidence with the axis of
rotation.
These sensors which can be of any suitable nature are, in the
embodiment of the invention, of the "measuring systems"
electromagnetic type of the U.S. company Kaman and they include a
sensing head associated with an electronic circuit. They enable the
position of a conducting part to be known with precision whose
distance modifies the impedance of a coil situated in the head and
this, within a range of the order of 1 millimeter.
The arrangement of these sensors associated with the induction
variation control members on the stator magnetic rings enables the
operation of the invention as emerges from FIGS. 4 and 5.
In these figures, where the centering members 2, 3 on the rotor
side and the centering members 4-5 on stator side will be found,
there have been arranged two sensors 34, 35 for correction of the
axis and two series of two sensors each for the alignment, one 36,
37 along the x axis, the other 38, 39 along the y axis, these axes
being at right angles to each other. The conducting part moving
under the head of the sensors is a conducting ring 40 and the
angular reference mark is provided by a slight conducting
over-thickness (such as an adhesive foil 41 for example) arranged
axially on said ring 40.
In a way, the signals resulting from the exploration of the space
F, by the sensors 34, 35 during the rotation, are of sinusoidal
shape whose amplitude is a function of the separation between the
axis of inertia and the rotor axis and the angular reference
marking can be reproduced on the sinusoidal signal by the reference
mark 41 producing a pulse signal. These signals are applied to an
integrating amplifier 42 which delivers the magnetic field
modifying orders to the centering members 4, 5 which then act,
according to the solution adopted, either on the motors 33, or on
the coils 23 so that by data processing or by repetition, the
separations are cancelled.
The alignment centering members 36, 37 at x and 38, 39 at y operate
similarly in order to determine, through an amplifier 43, this
space G defining along the two axes concerned x and y, the
alignment of the axis of rotation of the body 1 or 7, in order to
apply thereto the desired corrections.
As previously indicated, the correcting means may be applied
independently or conjointly according to the expressed needs.
Thus, if the correction is only aimed at the placing of the rotor
axis and the inertia axis in coincidence, the excentric rings are
only on the rotor and the centered rings on the stator whereas if
the correction is only aimed at orientation of the axis of
rotation, it is the excentric rings which are on the stator and the
centered rings on the rotor, the two systems being a fortiori
applicable conjointly, in accordance with FIGS. 6A, 6B, 6C and
6D.
By way of example, for a rotor 7 according to FIG. 5 of weight 6 kg
rotating at 20,000 rpm, the correction along F or G can be brought
to a value less than 0.1 micron, by means of the aforementioned
sensors.
It must be noted, in addition, that the energy necessary for the
application of the correcting means according to the invention can
be drawn from the rotation itself of the rotary body through a
generator keyed to the rotary axle, which, in this case, can be
considered as an "auto-correction" application of the system.
In general, the invention is directed to a method of balancing
rotary bodies with passive radial and active axial magnetic
suspension and of orienting their axis of rotation and it is
obvious that, in this spirit, any means which could be applied,
both for practicing this method and for adapting it within the
scope of the invention, would remain in the spirit of this
invention.
It is self-evident, in fact, that the present invention has only
been described and shown by way of preferred example and that
equivalents could be applied thereto, in its constituent elements
without however departing from the scope of said invention, as
defined in the following claims.
Thus, in particular, the invention can be applied, in the same
spirit, to a magnetically suspended body but whose speed of
rotation is zero in the case where it is desired to obtain only the
orientation of the axis of symmetry, for example, of a
seismograph.
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